Case Presentation: A 66-year-old female with pan-hypogammaglobulinemia from therapies for stage IV diffuse large B-cell lymphoma (DLBCL) and psoriatic arthritis on aprimelast presented with 6 months of severe diarrhea and hypokalemia. She achieved complete remission of DLBCL with R-CHOP and CAR-T therapy 15 and 8 months before symptom onset, respectively. Severe pan-hypogammaglobulinemia was detected 3 [...]